1. Field of the Invention
The present invention relates to a timepiece such as a portable timepiece which has within a case a rotated body to be rotated through operation outside the case constituting the exterior member and which has a stopper means preventing inadvertent rotation of this rotated body.
2. Description of the Related Art
Conventionally, there has been know a timepiece in which some measures are taken to prevent a malfunction of an in-revolving ring arranged so as to be rotatable along the peripheral edge of a dial within an exterior case, that is, inadvertent rotation of the in-revolving ring while, for example, the timepiece is being carried about (See, for example, Patent Literature 1 (JP-A-2010-139399)).
In the timepiece disclosed in Patent Literature 1, the case band of the case is provided with an engagement/disengagement means which, as an operation member moves, is engaged with or disengaged from an in-case end portion (hereinafter referred to as the inner end portion) of a pipe extending through the case band and fixed in position, and an in-revolving ring within the case. The operation member can be pushed and drawn with the head portion thereof pinched, and is urged toward the exterior of the case by a coil spring.
The engagement/disengagement means is composed of a drive transmission gear having teeth radially protruding from the outer periphery of the inner end portion of the pipe, and a drive gear which is formed on the back surface of the in-revolving ring and with and from which the drive transmission gear is engaged and disengaged through axial movement of a rotational operation portion.
In the timepiece disclosed in Patent Literature 1, in the state other than during the rotation of the in-revolving ring, the drive gear is separated from the drive transmission gear, so that inadvertent rotation of the operation member is not transmitted to the in-revolving ring. However, in the state in which the operation member is pushed toward the exterior of the case by the coil spring, it is possible to intentionally rotate the operation member; in this case, the operation member only idles, and cannot conjunction-move the in-revolving ring, so that there is a fear of the user thinking something is wrong with the timepiece.
Further, when a shock is applied to the timepiece, it is difficult to correctly maintain the still state of the in-revolving ring, so that, in rotating the in-revolving ring, when the user pushes in the operation member to bring the drive gear into mesh with the drive transmission gear, there is a fear of the drive gear hitting an end portion of the drive transmission gear, causing defective mesh-engagement between the drive gear and the drive transmission gear.
In this connection, there is known a timepiece with a stopper means which, while constantly maintaining the mesh-engagement between the drive gear and the drive transmission gear, prevents inadvertent rotation of the in-revolving ring and idling of the operation member when, for example, the timepiece is being carried about (See, for example, Patent Literature 2 (JP-A-2011-185835)).
In the timepiece of Patent Literature 2, the end portion situated outside the case (hereinafter referred to as the outer end portion) of a pipe extending through the case band of the case and fixed in position, and the head portion of an operation member inserted into the pipe, are provided with a stopper means engaged and disengaged as the operation member moves. The operation member allows rotation and pushing and drawing with its head portion being held, and is urged in the axial direction by a spring member. A drive gear is fixed to the shaft portion of the operation member, and this gear constantly maintains a state in which it is in mesh with tooth portions of an in-revolving ring in the case. Thus, through the rotation of the operation member, it is possible to rotate the drive gear.
In Patent Literature 2, the stopper means is arranged outside the case, and this means is composed of a lock gear having outer teeth radially protruding from the outer periphery of the outer end portion of the pipe, and an engagement ring mounted to the inner peripheral surface of the head portion of the operation member. The engagement ring has inner teeth engaged and disengaged with and from the outer teeth of the lock gear. Normally, due to the urging force of the spring member, the operation member is arranged at a first position where the outer teeth and the inner teeth are engaged (in mesh) with each other, whereby inadvertent rotation of the operation member is prevented. By axially moving the operation member against the urging force of the spring member to a second position where the outer teeth and the inner teeth are disengaged from each other, it is possible to rotate the operation member.
In a timepiece in which the stopper means is arranged outside the case as described above, the stopper means is rather poor in weathering performance, so that this means is easily exposed to human sweat, wind and rain, dust, etc., which means the means is subject to corrosion. Further, the engagement ring of the stopper means is mounted to the inner side of the head portion of the operation member, so that there is a fear of the head portion being increased in diameter. An increase in the diameter of the head portion is not compatible with the promotion in the reduction in the thickness of the case. At the same time, an increase in the diameter of the head portion leads to a reduction in operational torque, whereas the head portion gets easily caught by the edge of the trouser pocket when the timepiece is being carried about, which is not desirable.